Sources of sharia

Various sources of sharia are used by Islamic jurisprudence to elucidate the body of Islamic law. The primary sources, accepted universally by all Muslims, are the Qur'an and Sunnah. The Qur'an is the holy scripture of Islam, believed by Muslims to be the direct and unaltered word of God. The Sunnah consists of the religious actions and quotations of the Islamic prophet Muhammad and narrated through his Companions and the Imams (per the beliefs of the Sunni and Shi'ite schools respectively).

As Islamic regulations stated in the primary sources do not explicitly deal with every conceivable eventuality, jurisprudence must refer to resources and authentic documents to find the correct course of action. According to Sunni schools of law, secondary sources of Islamic law are consensus, the exact nature of which bears no consensus itself; analogical reason; pure reason; seeking the public interest; juristic discretion; the rulings of the first generation of Muslims; and local customs.Hanafi school frequently relies on analogical deduction and independent reasoning, and Maliki and Hanbali generally use the Hadith instead. Shafi'i school uses Sunnah more than Hanafi and analogy more than two others. Among Shia, Usuli school of Ja'fari jurisprudence uses four sources, which are Qur'an, Sunnah, consensus and the intellect. They use consensus under special conditions and rely on the intellect to find general principles based on the Qur'an and Sunnah, and use the principles of jurisprudence as a methodology to interpret the Qur'an and Sunnah in different circumstances. Akhbari Ja'faris rely more on tradition and reject ijtihad. According to Momen, despite considerable differences in the principles of jurisprudence between Shia and the four Sunni schools of law, there are fewer differences in the practical application of jurisprudence to ritual observances and social transactions.

...
Wikipedia